The goal of this project is to validate a novel enzymatic site-specific conjugation technique to develop antibody drug conjugate (ADC)s with better safety profile, wider therapeutic window and higher potency. ADCs that combine the target specificity of an antibody with the potent cell killing ability of a cytotoxic drug have shown considerable promise in cancer treatment. However, major improvements in ADC production is required as existing methods produce a heterogeneous mixture of ADCs with different number of drugs attached to different locations on the antibody. Each subpopulation of ADCs in such heterogeneous mixtures exhibit different pharmacokinetics, safety and efficacy profiles and limit the exploitation of their full therapeutic potential. Conjugation of drugs to specific sites on antibodies is currently being investigated to generate homogeneous ADCs. However, the methods that are currently explored require antibodies to be modified through point mutation (for direct chemical conjugation) or engineered tags (for enzymatic conjugation). These procedures are complicated and time consuming. In addition, these mutations may affect antibody stability and introduce immunogenicity. To overcome these limitations, we have developed a technology to site-specifically conjugate cytotoxic drugs to intact antibodies by employing engineered microbial transglutaminase (mTgase). A major advantage of our technology is that it allows us to generate homogeneous ADCs without the need to make any modifications to antibody structure. Our preliminary results demonstrate that engineered mTgase can catalyze site-specific conjugation of drugs to native, unmodified IgGs. The first ADC to be generated using our mTgase-mediated conjugation approach will be an anti-HER2 IgG ADC that will be used to treat HER2 overexpressing tumors. In preliminary studies, a panel of site-specific-anti-HER2 ADCs produced by our approach exhibited better stability and efficacy both in vitro and in vivo. In phase I studies, we will compare the stability, pharmacokinetics and anti-tumor efficacy of different site-specific anti-HER2 ADCs that we have generated in HER2 expressing tumor models to identify the most promising ADC candidate. In Phase II studies, we will perform the preclinical evaluation of our ?lead? ADC candidate to enable IND filing and further clinical trials. We believe that the successful completion of these studies will transform the ADC field and will substantially cut down the cost and time required for ADC production.